This invention relates to an hydraulic valve system utilized to control the flow of a normally gaseous liquid, and more particularly, to control the flow of anhydrous ammonia to a metering apparatus used in conjunction therewith.
Anhydrous ammonia is a normally gaseous fluid at atmospheric conditions which can be easily stored under pressure as a liquid in any suitable container such as a conventional pressurized vessel. Once released from a pressurized state to ambient conditions the anhydrous ammonia flashes to a gaseous state. One of the uses of anhydrous ammonia is as an agricultural fertilizer. When utilized in this manner, anhydrous ammonia is carried in a pressurized vessel which is fluidly connected to a propelled earth drilling apparatus. A slit is formed in the ground by the drilling apparatus, and the anhydrous ammonia is injected underground. The flow of anhydrous ammonia to the drill is controlled by a valve and a metering apparatus. The valve controls the flow of anhydrous ammonia to the metering apparatus and the metering apparatus controls the amount of flow to the fertilizing knives.
When dispensing anhydrous ammonia in the field, there is a need for remotely controlling the flow of the same from the vehicle both for safety and for conserving time. Since ammonia when in the liquid state can cause burns and when in the gaseous state is extremely irritating to the skin, a need exists for an effective and reliable control system for the valve. Prior art attempts to provide such a system include, for example, remotely controlled, mechanically actuated valves. But such valves are not suited to the needs afore described since the valves are set in the open position and constructed to be closed by mechanical actuation thereby creating an inherent hazard of a closing malfunction. Further, solenoid valves have been utilized (see for example U.S. Pat. No. 3,698,682) but solenoid valves are dependant upon the absence of electrical malfunctions and possess the liabilities of not being easily repaired in the field and requiring modification of conventional metering apparatus to be used in conjunction therewith.